Electrodeposited copper foil with a carrier foil has hitherto been used as basic materials for the manufacturing of printed wiring boards which are widely used in the field of the electrical and electronic industries. This electrodeposited copper foil with a carrier foil is bonded to a polymer insulating substrate, such as a glass-epoxy substrate, a phenol substrate and a polyimide, by hot pressing to form a copper-clad laminate, and is used in the manufacturing of printed wiring boards.
This electrodeposited copper foil with a carrier foil is thermocompressed to an B-stage cured prepreg by applying a high pressure in a high-temperature atmosphere (hereinafter this step is referred to as “press forming”), thereby preventing wrinkles from occurring in a copper foil layer during the manufacturing of a copper-clad laminate and hence making it possible to prevent the formation of cracks in the copper foil in wrinkle areas and to prevent the exudation of resin from the prepreg. And this makes it easy to form a thin copper foil layer on the surface of the copper-clad laminate.
In general, this electrodeposited copper foil with a carrier foil can be broadly divided into a peelable type and an etchable type. In a word, the difference is as follows. In the peelable type, the carrier foil is removed by peeling after press forming, whereas in the etchable type, the carrier foil is removed by an etching method after press forming.
In the peelable type, the value of peel strength of the carrier foil is very unstable after press forming. In an extreme case, the situation is such that the peelable type has the drawback that the carrier foil cannot be peeled and that the aimed peel strength cannot be easily obtained. In order to solve this problem, as electrodeposited copper foil with a carrier foil which eliminates the drawback of the conventional electrodeposited copper foil with a carrier foil of the peelable type and can stabilize the peel strength of an interface between the carrier foil and the electrodeposited copper foil at a low level, the present inventors have proposed electrodeposited copper foil with a carrier foil, as disclosed in the Japanese Patent Laid-Open No. 2000-309898, which is characterized in that in electrodeposited copper foil with a carrier foil in which an adhesive interface layer is formed on the surface of the carrier foil, copper is electrodeposited on this adhesive interface layer and this deposited copper layer is used as the electrodeposited copper foil, an organic agent is used in this adhesive interface layer.
However, an adhesive interface layer of the electrodeposited copper foil with a carrier foil which the present inventors have proposed was formed by causing an organic agent constituting the adhesive interface layer to be adsorbed on a surface of the carrier foil by use of an aqueous solution containing only this organic agent. This carrier foil-incorporated electrodeposited copper layer shows excellent performance at pressing temperatures of about 180° C. in the case of use of an ordinary FR-4 prepreg, and even after press forming the carrier foil can be very easily peeled.
However, recent years have seen increasing requirements for the downsizing of electronics and electric machinery and apparatus without showing any sign of an end to this trend, and multilayer design of printed wiring boards, which are the basic parts of electronics and electric equipment, high density design of copper foil circuits, and high density packaging design of mounted parts have been required more strongly than before. In such a case, because the quantity of heat released from mounted parts increases, printed wiring boards as built-in parts are also required to provide high heat resistance and hence highly heat resistant substrates such as a substrate using a BT resin, a fluoroplastic substrate and a polyimide substrate have come to be used. It is inevitable to adopt pressing temperatures exceeding 200° C. as the pressing temperature of copper-clad laminates using these substrates and the pressing temperature tends to become higher.
In recent markets, it has been required to provide the characteristic that even after laminating at pressing temperatures of not less than 300° C., the carrier foil can be easily peeled from the surface of a copper-clad laminate. It was a fact that when the electrodeposited copper foil with a carrier foil which the present inventors have hitherto proposed is press worked at temperatures of not less than 300° C., the peeling of the carrier foil is not stable, with the result that the phenomenon that the carrier foil cannot be peeled occurs. Therefore, the markets have demanded electrodeposited copper foil with a carrier foil of the peelable type excellent in high-temperature heat resistance which permits easy peeling of carrier foil even in the case of press working at temperatures of not less than 200° C. (hereinafter referred to as “electrodeposited copper foil with a carrier foil for high-temperature heat-resistance” in this specification).